Combustion chambers with a number of burner elements distributed around the periphery of a substantially annular combustion space are known by the designation "annular combustion chambers".
Compared with separate combustion chambers, annular combustion chambers have the advantage that they make possible a more compact overall design of the gas turbine. The smaller dimensions result generally in cost advantages in production. The smaller surfaces of an annular combustion chamber also results in the cooling problems being more controllable. The disadvantages of this conventional design arise from the necesssity of dividing the output over individual burner elements, particularly if oil atomization and oil supply are problematical. Another disadvantage is also the difficulty of achieving an even a temperature distribution within a short operating length.
An annular combustion chamber is known from Swiss Pat. No. 585,373 which is provided with a number of swirl members arranged centrosymmetrically at its air inflow-sided and face-sided end. These swirl members are in each case disposed in pairs and it is evident that the swirl members can generate swirl flows with opposed senses of rotation. Also emerging from this publication is the interaction of the burner elements with the swirl members, it being possible for burner element and swirl member to be integrated in a premixing pipe. Nevertheless, the swirl members are arranged such that the individual swirl jets or swirl flows can only influence each other slightly.
It can be seen from the technique proposed by the Swiss patent that the desired irrotational flow with an even overall pressure cannot be produced within the combustion chamber length. An even temperature distribution at the turbine inlet is thus not ensured. Admittedly this disadvantage could be counteracted by a corresponding extension of the combustion chamber length. Nevertheless, this measure would mean that other disadvantages would have to be accepted. For instance, the structural engineering disadvantages caused by the extension of the combustion chamber length. However, of greater significance here is the impossibility of meeting the legislated limits on NO.sub.x emissions. The reason for this problem is that low No.sub.x emission values, disregarding the influence of an excessively high temperatures can only be maintained if the retention time of the gas particles in hot oxygen-free zones is as short as possible, namely no longer than a few milliseconds.
On the other hand, so that low CO emission values can be achieved, it is not permissible to drop below a certain limit temperature in the reaction region. This requirement sets a limit on small design sizes.
These requirements are not met without the existence of an intensive reciprocal mixing of various swirl flows, as there is the imminent danger here that the gas particles remain too long in the region of hot oxygen-free zones or subsequently are swirled back there, which has negative effects on the NO.sub.x emission values. The other danger is that the temperature in certain regions could drop below the limit temperature responsible for the CO emission values. In addition, it is known that the avoidance of NO.sub.x can be achieved with combustion chamber concepts with staged combustion. This staging may mean either an under-stoichiometric primary combustion zone with subsequent postcombustion at low temperatures or the staged switching-in of over-stoichiometric operated burner elements, for example premixing burners with increasing load. In any case, the staging also requires a powerful mixing mechanism to avoid the abovementioned problems. Thus, for example the supply of swirl free jets in a combustion chamber, as is the case with the postcombustion from the above Swiss Patent Specification, does not provide adequate mixing over a short stretch.